Platelet-Mediated Cardioprotective Effect Against Ischemia-Reperfusion Injury in Isolated Rat Hearts: Role of Platelet Number and Contribution of Supernatant of Aggregated Platelets

Abstract

Background: Previous studies have documented cardioprotective effects of circulating platelets after reperfusion injury. The present study was designed to examine the role of platelet number and the contribution of platelet-released mediators in the platelet superna tant in cardioprotection against ischemia-reperfusion-induced myocardial dysfunction. Methods and Results: Isolated buffer-perfused (constant volume) Sprague-Dawley rat hearts were subjected to 25 minutes of global ischemia followed by 30 minutes of reperfu sion. Ischemia-reperfusion resulted in myocardial dysfunction, indicated by an increase in coronary perfusion pressure and left ventricular end-diastolic pressure, and a decrease in de veloped left ventricular pressure. Perfusion of hearts with washed rat platelets (103-2.2 × 107 cells/mL) significantly ( P < .01) attenuated these indices of myocardial dysfunction upon ischemia-reperfusion in a concentration-dependent manner. A cardioprotective effect of platelets was observed at a concentration as low as 105 platelets/mL. Similar cardioprotec tion was seen in hearts perfused with the supernatant of aggregated platelets. Conclusions: These observations indicate that the platelet-mediated cardioprotective effect against ischemia-reperfusion in vitro is concentration dependent, and platelet-released mediators in the platelet supernatant are protective against ischemia-reperfusion injury.